High molecular weight ethylene-based polymers are known to possess a number of advantaged performance properties, such as, for example, increased tensile strength, increased ability to be filled with a range of additives, and improved compression set. In a solution polymerization process, the polymer is dissolved typically in a non-reactive solvent, producing a polymer stream that is transferred throughout the process via multiple pumps. In such a process, the resulting viscosity of the polymer stream becomes prohibitively high to transfer the high molecular weight polymer through the process. Transfer of the polymer stream becomes even more of a challenge once the bulk of the solvent is removed in the devolatilization process.
There is a need for new, energy efficient polymerization processes for the formation of high molecular weight ethylene-based polymers. There is a further need for such high molecular weight polymers.
U.S. Publication 2009/0076216 discloses a process for a fluid phase, in-line blending of plasticized polymers. The process includes providing two or more reactor trains configured in parallel, and a separator for product blending and product-feed separation. The one or more of the reactor trains produce one or more polymers, and one or more of the reactor trains produce one or more plasticizers. Suitable plasticizers include polyalphaolefin oligomers, polybutenes, low glass transition temperature polymers and combinations thereof.
U.S. Pat. No. 7,759,415 discloses a method to make an article comprising the steps of combining a semi-amorphous polymer, having a heat of fusion of less than 70 J/g, with a plasticizer, and optionally one or more additives, to produce a polymer concentrate; combining the polymer concentrate with one or more final materials, to produce an article precursor; and forming the article at least partially from the article precursor. The polymer concentrate is disclosed as having no visible phase separation, as demonstrated by the polymer concentrate having no visually detectable loss of the plasticizer, after a portion of the polymer concentrate is aged on an absorbent surface for 24 hours at 25° C.
U.S. Pat. No. 5,552,489 discloses tackifiers having number average molecular weights of 5,000 or less, and glass transition temperatures above 0° C. The tackifiers are produced by combining a single site catalyst with an alpha-olefin and a cyclic monomer, under conditions designed to produce low molecular weight.
U.S. Pat. No. 6,271,311 discloses extruded shapes, profiles, and parts, in general, based on an ethylene, alpha-olefin elastomeric polymers that are manufactured utilizing a tailored approach to polymerization. The ethylene, alpha-olefin elastomeric polymer has a broader molecular weight distribution than generally available from metallocene catalyzed elastomeric polymers.
European Patent EP 1472295B1 discloses synthetic polymers, generally with improved balance of processability, resilience and durability. These polymers are generally of the ethylene, alpha-olefin, diene terpolymer type.
Additional polymers and polymerization process are disclosed in the following: U.S. Pat. Nos. 3,884,993, 6,120,887, 6,114,457, 6,147,180, 6,319,998, 5,359,015, 7,531,601; U.S. Publication 2008/0125547; and International Publication Nos. WO 97/29138 and WO 11/008837.
There remains a need for high molecular weight ethylene-based polymer compositions with lower viscosities, and thus, improved processabilities. There is also a need for energy efficient polymerizations for the formation of such high molecular weight ethylene-based polymers. These needs and others have been met by the following invention.